Let’s see how the unit works. On pressing the push button S, the
The electronic gadget described in this article is a compromise
between these two possibilitiesh lt connected in series to the radio as
supply (6-l2 volts). As soon as the commercials start press the push
button (See Fig) momentarilyi on doing so, thesiipply to the
transistor radio gets cut for 21 certain period which can be adjusted.
Usually the commercisls lust fora minute or so and therefore the off
time ot” the gadget cnn be set tor l minute. After the lapse oi`}
minute, the device automatically switches on the supply to the
transistor and the radio programme is restored.
capacitor C gets chztrgmi through 15 ohm resistance. Till the time
capacitor stays charged. transistor Q1 stays non-conductive. Since
Q1 is non—conductive, there is no base bias at Q2 and hence no
current flows through Q-:. The discharging path of the condenser is
determined by a fixed and variable resistor connected in parallel
to it. Higher the resistance, slower is the discharging and longerjs
” the time delay. A diode is included in the base circuit so that the
discharging takes place only through the resistor. When the charge
across the condenser falls to
a low value, Q1 comes into conduction
which in turn brings Q2 into conduction and hence power to the
transistor is restored. For higher time delays higher values of con-
denser and/or higher values of a resistance can be selected. A
l After wiring the complete unit connect a small bulb across the
output and switch on the supply. The bulb should lighttupj Now
press S momentarily. The bulb should go off ani should stay oil`
for a small timeiafter which it should again light up. After the
setting of the time, connect theiunit to the radio transistor battery `
Parts Required for making a simple commercial mute feature circuit:
I. Transistors :— Ac 188 – INO. AC 127 1;No`.` ”
2. Diodes OA 8`5 1. No.
3. Coridciisérf-‘ 11000 mid 12 volt 1 No,
4.1 Rcsistzmcés 1;/2 watt) 1Ki ’ 3ANos.
A 15 ohms lN0.
5, ·Pot‘10 K lin. 1No
6, °Push`-on switch‘1 No.